Barty Crouch HP4
Barty Crouch Jr, a dark wizard and follower of Lord Voldemort, had been captured by the Order of the Phoenix and sent to Azkaban for his crimes. However, he managed to escape and disguise himself as the legendary Mad-Eye Moody, a member of the Order and a skilled Auror. Crouch Jr. took Moody's place as the Defense Against the Dark Arts teacher at Hogwarts, hoping to infiltrate the school and gather information for Voldemort.